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Gill EROD in monitoring of CYP1A inducers in fish: A study in rainbow trout (Oncorhynchus mykiss) caged in Stockholm and Uppsala waters
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Physiology and Developmental Biology, Environmental Toxicology.
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2007 (English)In: Aquatic Toxicology, ISSN 0166-445X, E-ISSN 1879-1514, Vol. 85, no 1, 1-8 p.Article in journal (Refereed) Published
Abstract [en]

The gill filament 7-ethoxyresorufin O-deethylase (EROD) assay was evaluated as a monitoring tool for waterborne cytochrome P4501 A (CYP1A) inducers using rainbow trout (Oncorhynchus mykiss) caged in urban area waters in Sweden. To compare the CYP1A induction response in different tissues, EROD activity was also analyzed in liver and kidney microsomes. Immunohistochemistry was used to localize CYP1A protein in gill and kidney. In two separate experiments fish were caged at sites with fairly high expected polyaromatic hydrocarbon (PAH) contamination. In the first experiment, gill EROD activities were analyzed in fish exposed for 1-21 days in a river running through Uppsala. The reference site was upstream of Uppsala. In the second, gill, liver and kidney EROD activities were analyzed in fish exposed for 1-5 days in fresh or brackish waters of Stockholm and in a reference lake 60 km north of Stockholm. Fish exposed for 5 days followed by 2 days of recovery in tap water in the laboratory were also examined. The gill consistently showed a higher EROD induction compared with the liver and the kidney. After I day of caging, gill EROD activity was markedly induced (6-17-fold) at all sites examined. Induction in gill was pronounced (5-7-fold) also in fish caged at the reference sites. In the 21-day exposure study gill EROD activity remained highly induced throughout the experiment (26-fold at most) and the induced CYP1A protein was exclusively confined to the gill secondary lamellae. In the 5-day exposure experiment, EROD activity peaked after I day and then declined in both gill and liver, while CYP1A immunostaining in the gill remained intense over the 5-day period. In the kidney, CYP1A staining was weak or absent. We conclude that gill EROD activity is a more sensitive biomarker of exposure to waterborne CYP1A inducers than EROD activity in liver and kidney.

Place, publisher, year, edition, pages
2007. Vol. 85, no 1, 1-8 p.
Keyword [en]
fish; gill; CYP1A; EROD; monitoring
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-95923DOI: 10.1016/j.aquatox.2007.07.013ISI: 000250181300001OAI: oai:DiVA.org:uu-95923DiVA: diva2:170303
Available from: 2007-05-09 Created: 2007-05-09 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Gill EROD Activity in Fish: A Biomarker for Waterborne Ah-receptor Agonists
Open this publication in new window or tab >>Gill EROD Activity in Fish: A Biomarker for Waterborne Ah-receptor Agonists
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Induction of the cytochrome P450(CYP)1A protein and the connected increase in 7-ethoxyresorufin O-deethylase (EROD) activity are common biomarkers in fish. Enhanced activity of this protein signals exposure to Ah-receptor agonists such as chlorinated dioxins, co-planar polychlorinated biphenyls (PCBs) and certain polycyclic aromatic hydrocarbons (PAHs). The EROD biomarker is commonly analyzed in liver microsomes. However, the gill is directly exposed to waterborne pollutants, and in this thesis the gill filament EROD assay was therefore evaluated as a monitoring tool for waterborne CYP1A inducers in fish. Originally developed in rainbow trout (Oncorhynchus mykiss), the assay was here applied in various limnic and marine species. Following exposure to low waterborne concentrations of the readily metabolized CYP1A inducers benzo(a)pyrene (BaP) and indigo, a strong EROD induction was observed in the gill but not in the liver. This likely reflected metabolic clearance of the inducers in gill and other extrahepatic tissues. The high sensitivity of the gill was confirmed in studies of fish caged in waters in urban and rural areas in Sweden where the gill consistently showed a more pronounced EROD induction compared with the liver and the kidney. Fish caged in the reference waters showed surprisingly strong gill EROD induction and CYP1A immunostaining. Consequently, there may be CYP1A inducers present in the aquatic environment that are not yet identified. The assay was further applied in Atlantic cod (Gadus morhua) as a biomarker of exposure to crude oil and produced water (PW) from oil fields in the North Sea. The assay was finally adapted to detect inhibiting compounds, and an imidazole, a triazole and a plant flavonoid turned out to be potent gill EROD inhibitors. The overall conclusion from the studies of this thesis is that the gill filament EROD assay is a practical and sensitive biomarker of exposure to waterborne CYP1A inducers in various fish species. The induction of gill EROD activity in fish also at the reference sites in the field studies calls for further studies on background contamination in Swedish waters.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 52 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 311
Keyword
Biology, biomarker, fish, gill, CYP1A, EROD, environmental monitoring, induction, inhibition, PAH, PCB, produced water, Biologi
Identifiers
urn:nbn:se:uu:diva-7899 (URN)978-91-554-6902-3 (ISBN)
Public defence
2007-06-02, Lindahlsalen, Evolutionsbiologiskt centrum (EBC), Norbyvägen 18 A, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2007-05-09 Created: 2007-05-09 Last updated: 2009-04-02Bibliographically approved
2. Evaluation of Biomarker Responses in Fish: with Special Emphasis on Gill EROD Activity
Open this publication in new window or tab >>Evaluation of Biomarker Responses in Fish: with Special Emphasis on Gill EROD Activity
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many chemicals present in the aquatic environment can interfere with physiological functions in fish. Exposure to chemicals can be revealed by the use of biomarkers. Induction of 7-ethoxyresorufin O-deethylase (EROD) activity is a commonly used biomarker for exposure to CYP1A inducers such as dioxins and polyaromatic hyrdrocarbons. Vitellogenin is a frequently used biomarker for estrogenic compounds in various fish species whereas a biomarker for androgens, spiggin, is only found in sticklebacks. The main objectives of this thesis were to evaluate gill EROD activity as a biomarker and the three-spined stickleback as a model species in ecotoxicological studies.

EROD activities were measured in gill, liver and kidney in rainbow trout (Oncorhynchus mykiss) caged in urban areas in Sweden. EROD induction was most pronounced in the gill. Also in fish caged at reference sites, with an expected low level of known CYP1A inducers, a marked gill EROD induction was found. One suggested inducer in rural waters is humic substances (HS). To evaluate the EROD-inducing capacity of HS, three-spined sticklebacks (Gasterosteus aculeatus) were exposed to HS of natural or synthetic origin. Both kinds of HS caused significant EROD induction. Gill EROD activities were also induced in sticklebacks exposed to ethynylestradiol (EE2) and β-naphthoflavone (βNF), alone and in combinations. Production of vitellogenin was induced in sticklebacks exposed to ≥50 ng EE2/l and a significant decrease in spiggin production was observed in individuals exposed to 170 ng EE2/l.

Results from this thesis further strengthen the contention that gill EROD activity is a very sensitive biomarker for CYP1A inducers and that the stickleback is a suitable biomonitoring species, especially for exposure to CYP1A inducers. The finding that not only classical CYP1A inducers but also HS and high EE2 concentrations stimulate gill EROD activity is of significance for the interpretation of biomonitoring data.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 59 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 345
Keyword
Biology, three-spined stickleback, biomarker, EROD, ethynylestradiol, gill, vitellogenin, spiggin, CYP1A inducers, humic substances, sperm quality, biomonitoring, Biologi
Identifiers
urn:nbn:se:uu:diva-8222 (URN)978-91-554-6975-7 (ISBN)
Public defence
2007-10-19, Lindahlsalen, EBC, Norbyvägen 18A, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2007-09-28 Created: 2007-09-28 Last updated: 2011-01-27Bibliographically approved

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